A former McDonalds worker has filmed a live mouse rummaging around in a bag full of Big Mac burger baps saying his manager ordered employees to serve them despite the rodent.

Karrium Demaio, who no longer works in the fast-food chain in Philadelphia allegedly shot the footage back in November and the footage clearly shows a mouse inside the bag of buns.

Demaio said he released the footage to the news because he wanted to warn customers saying this instance was one of many whilst he worked there.

"That wasn't the first time," he said. "That was about the sixth or seventh time. That's what made me like; I got to get video of this."

"I was going back there to get something else and I heard some rustling, so I turned around, and I look, I seen a mouse inside the bread. Not on top of the package, but inside of the package."

I was working there from October of 2010 to January of this year. There hasn't been a time when we couldn't go in the back and not see mouse droppings on the bread.

He said that despite knowledge of the rodent in the bag, his manager still ordered him to brush off the droppings and serve the bread to unsuspecting customers.

One of Demaio's colleagues confirmed the video and his version of the story.

Ken Youngblood, who owns the McDonalds franchise, said: "After viewing the video, we are going to continue to investigate this claim to make certain we have all the facts. I want my customers to know that I am taking this matter seriously and will immediately address any issues that may exist. Therefore, if necessary, we will work with the appropriate authorities to get the facts."